Britain is launching a fresh diplomatic bid to ease tensions in the Gulf and prevent the Iran nuclear deal unravelling, after recent provocations.
The UK Foreign Secretary Jeremy Hunt will travel to Brussels on Monday for a meeting of EU foreign ministers to seek support from the European signatories to the agreement - France and Germany.
In a joint statement ahead of the meeting, the three European powers said they were "deeply troubled" by recent events in the region and urged the US and the Iran to draw back from conflict.
"We believe the time has come to act responsibly and seek a path to stop the escalation of tensions and resume dialogue," the statement said.
"The risks are such that it is necessary for all stakeholders to pause and consider the possible consequences of their actions."
Mr Hunt's visit comes after he offered to help secure the release of the Iranian supertanker Grace 1 held in Gibraltar after being detained in an operation involving British Royal Marines.
In a telephone call with Iranian foreign minister Mohammad Javad Zarif on Saturday, Mr Hunt sought to reassure him the vessel was intercepted over suspicions it was carrying oil to Syria - and not because it was Iranian.
He said he had offered to facilitate the tanker's release in return for guarantees from Tehran that it would not breach EU sanctions on the Assad regime.
The move comes amid heightened tensions in the Gulf following Donald Trump's decision to unilaterally withdraw the US from the nuclear deal.
Last week, a Royal Navy warship intervened to drive off Iranian patrol boats after they approached a British tanker as it sailed through the Strait of Hormuz.
It prompted fears the Iranians were trying to seize a UK ship in retaliation for the detention of the Grace 1.
In recent weeks, the US has sent thousands of troops, an aircraft carrier, nuclear-capable B-52 bombers and advanced fighter jets to the Middle East.
Iran, meanwhile, has begun exceeding limits on uranium enrichment agreed in the 2015 deal amid frustration in Tehran at the return of crippling US economic sanctions.
Ahead of the meeting in Brussels, Mr Hunt said: "The Middle East is already one of the most unstable regions in the world, but if the different parties were armed with nuclear weapons it would represent an existential threat to mankind. I will do everything in my power to prevent that from happening.
Australian Associated Press
